The pronounced l=0 selectivity of the (e,e’p) proton knockout reaction has been exploited to determine the relative occupation of the 3$s_{1/2}$ proton orbit in ${}_{}{}^{205}{}_{}{}^{}\mathrm{Tl}$ and ${}_{}{}^{206}{}_{}{}^{}\mathrm{Pb}$. This value, when combined with previous electron scattering data, enables us to extract in a largely model-independent fashion the absolute 3$s_{1/2}$ occupation probability in ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$. The depletion of the 3$s_{1/2}$ proton orbit is found to be (18±9)%, compatible with predictions of many-body theories.

We report the observation of the giant dipole resonance in Pb nuclei near A∼200 at excitation energies of 66, 88, and 103 MeV and with average angular momenta of 25ħ to 44ħ. The fits to the dipole strength distribution require two components indicating a strongly deformed nuclear shape. Using width parameters consistent with the ground-state systematics of heavy deformed nuclei gives $E_1$=11.9 MeV, $E_2$apeq215.6 MeV, and prolate deformation with βapeq20.3. These results are compared with a prediction for superdeformed shapes in ${}_{}{}^{196}{}_{}{}^{}\mathrm{Pb}$ at L=30ħ.

A new manifestation of the Berry phase is presented in theory of fast-rotating superfluid nuclei: diabolic pair transfer, i.e., oscillation of the pair-transfer matrix elements as a function of the angular velocity, is shown to be the direct consequence of the Berry phase, giving a nontrivial contribution at the diabolical points of cranked Hartree-Fock-Bogoliubov spectra.

Several rotational bands have been populated to high spin in the γ-soft nucleus ${}_{}{}^{131}{}_{}{}^{}\mathrm{La}$. We present expreimental evidence for a collective oblate rotational band based on a π${\mathrm{h}}_{11/2}$⊗(ν${\mathrm{h}}_{11/2}$${)}^2$ three-quasiparticle configuration. It is the rotational alignment of the pair of neutrons from the upper ${\mathrm{h}}_{11/2}$ midshell which drives the nucleus from a prolate (γ=0°) shape to a collectively rotating oblate (γ=-60°) shape. This band coexists with a prolate band that contains a pair of aligned protons from the lower ${\mathrm{h}}_{11/2}$ midshell.

We propose a new theory to treat fluctuation phenomena in heavy-ion reactions. In practical terms, the method is an extension of the theories of the one-body density based on mean-field plus collisional dynamics. In an exploratory study of the ${}_{}{}^{20}{}_{}{}^{}$Ne${+\mathrm{}}^{20}$Ne reaction, we find considerable fragmentation with a rapidly falling mass spectrum.

Inclusive and exclusive γ-ray spectra have been measured in the reaction ${}_{}{}^{40}{}_{}{}^{}\mathrm{Gd}$ at 44 MeV/nucleon. Impact-parameter selection has been provided by various coincidence conditions with a forward-angle particle detector. The γ yield for $E_{\gamma }$>25 MeV is consistent with emission from the nucleon-nucleon system and decreases strongly for larger impact parameters. Below 25 MeV, the photons originate from statistical decay of the excited fragments with a strength function dominated by giant resonances. The observed γ yields provide information on the excitation energies of the reaction products.

A universal, physically intuitive description of collectivity in heavy nuclei is obtained in terms of the parameter P=$N_p$$N_n$/($N_p$+$N_n$) which gives the average number of interactions of each valence nucleon with those of the other type. Regardless of mass region, deformation sets in when P=$P_{\mathrm{crit}\mathrm{\approxeq }4–}$5. This, in turn, gives a rule that medium-mass and heavy nuclei with effective $N_p$ or $N_n$≤4 cannot be deformed. An interpretation in terms of the monopole and quadrupole p-n interactions is discussed.

The structure of the very neutron-deficient Ge region has been investigated with use of particle-γ coincidence techniques in weak fusion-evaporation channels. Excited states up to spin (31/2) have been established in ${}_{}{}^{65}{}_{}{}^{}\mathrm{Ge}$, and five transitions have been assigned to the N=Z nucleus ${}_{}{}^{64}{}_{}{}^{}\mathrm{Ge}$. The first excited state in ${}_{}{}^{64}{}_{}{}^{}\mathrm{Ge}$ is at 902.1±0.8 keV. The ${}_{}{}^{65}{}_{}{}^{}\mathrm{Ge}$ level scheme provides the first indication in this mass region of a theoretically predicted softness with respect to octupole deformation.

Measurements have been made of single-neutron stripping and pickup in the system ${}_{}{}^{58}{}_{}{}^{}$Ni${+}^{208}$Pb at 10.3 and 17.4 MeV/nucleon. The complex spectra observed are found to be dominated by transfers from the valence shell of the donor to bound and unbound shells of the recipient. The data were analyzed with the distorted-wave Born approximation together with a dynamic polarization potential. The suggestion is made that the large yields seen at forward scattering angles may arise from increases in the real nuclear potential which might occur when a neutron jumps to an unoccupied major shell.

We show that dynamical symmetries other than the known U(5), SU(3), or O(6) limits of the interacting-boson model can be identified for some choices of the boson-Hamiltonian parameters. The recently discussed SO(7) symmetry is hereby completely accommodated within a boson framework. Our analysis shows that this symmetry is in fact characterized by a U(5) boson Hamiltonian accompanied by choices of transition operators which differ from the traditional choices.

A rotational band has been studied in ${}_{}{}^{132}{}_{}{}^{}\mathrm{Ce}$ to a spin above 50ħ. Lifetime measurements have resulted in a large quadrupole moment corresponding to a deformation β∼0.5. This is consistent with the moment of inertia determined from the energy-level spacing. These data are the first measurements of collectivity of discrete lines at high spin within the superdeformed second minimum.

Using projection techniques, we show that stretching occurs in the sdg interacting-boson model (IBM) but not in the sd model. As a result the sdg IBM allows g-factor variations in the ground-state band in accordance with recent experiments, and as such may provide a signature for the g boson.

Nucleon-transfer cross sections have been measured at subbarrier energies in collisions between Sn target nuclei and light ${(}^{16}$,18O) and heavy ${(}^{58}$Ni) projectile nuclei. Large differences in cross sections correlate directly with the subbarrier fusion enhancement, suggesting nucleon transfer as an important doorway to fusion with a direct dependence on the overall transfer strengths. Simple two-level mixing considerations support this picture.

The angular distribution of alpha particles with respect to the spin direction of the residual nuclei is used to probe the shapes of the emitting systems. Two compound systems have been studied: ${}_{}{}^{170}{}_{}{}^{}\mathrm{Yb}$ and ${}_{}{}^{110}{}_{}{}^{}\mathrm{Sn}$. Deformed emission shapes are required in order to understand the alpha-gamma correlations in the ${}_{}{}^{170}{}_{}{}^{}\mathrm{Yb}$ system, but not for the ${}_{}{}^{110}{}_{}{}^{}\mathrm{Sn}$ compound system. These conclusions are identical to those reached by the study of giant resonances built on excited states for very similar systems.

From the analogy between the collective quadrupole decay among compound nuclear states in strongly rotating nuclei and the phenomenon of nuclear magnetic resonance, it is possible to formulate a model of nuclear rotational damping which exhibits interesting correspondences between nuclear and atomic statistical processes.

In the angular correlation of the (${\pi }^{\mathrm{-}}$,pp) reaction, two rather sharp peaks were observed for ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ and C. These peaks were considered to be associated with two-step processes; one is pp-pp scattering after the (${\pi }^{\mathrm{-}}$,pn) reaction, and the other is the ${\pi }^{\mathrm{-}}$p-${\pi }^0$n reaction followed by the (${\pi }^0$,pp) reaction. The intranuclear cascade model reproduced very well the two peaks. These results show that two-step processes are important in pion-absorption reactions for light nuclei.

The ground-state charge densities of ${}_{}{}^{204}{}_{}{}^{}$,206,207,208Pb have been accurately determined by elastic electron scattering. Mean-field calculations fail to describe the individual charge densities in the central region of the nucleus. However, they properly account for polarization mechanisms in the nuclear interior, as they accurately describe the corresponding charge-density differences. We show that these data are sensitive to the value of the nuclear compressibility κ and that they are compatible with the value κ=230 MeV.

It is demonstrated that the ${\mathrm{\pi }}^0$/γ ratio can never be a definite signal of the quark-gluon plasma but may be a rather useful diagnostic of the plasma only if measured in combination with dileptons in the kinematic regime ${\mathrm{p}}_{\mathrm{T}}$≊2–4 GeV/c.

The analyzing-power behavior and the isospin dependence of the cross sections for near-threshold reactions ${}_{}{}^{13}{}_{}{}^{}$C(p,${\pi }^{\pm }$) and ${}_{}{}^{12}{}_{}{}^{}$C(p,${\pi }^{+}$) are compared with expectations from pion production measurements in free two-nucleon collisions. The general agreement for ($p_{\mathrm{pol}}$,${\pi }^{+}$) suggests that the stable analyzing-power pattern observed for ($p_{\mathrm{pol}}$,${\pi }^{\mathrm{-}}$) continuum transitions may reflect the as yet unmeasured free $p_{\mathrm{pol}\mathrm{n}\to \mathrm{pp}{\pi }^{\mathrm{-}}}$ behavior. We also discuss constraints imposed by quasifree ${\mathrm{NN}}_{\mathrm{pol}\to \mathrm{NN}\mathrm{\pi }}$ expectations on the interpretation of anomalous ($p_{\mathrm{pol}}$,${\pi }^{+}$) results for two strongly populated states at high excitation in ${}_{}{}^{13}{}_{}{}^{}$,14C.